Metal can paint providing coating retaining high adhesion even with lapse of time

Abstract

Disclosed is a paint for a can which comprises an epoxy resin component formed by condensation of a dihydroxyl compound with an epihalohydrin and a curing agent component, said epoxy resin component containing terminal α-glycol groups at a concentration of 0.05 to 0.60 equivalent per Kg of the resin. This paint provides a coating capable of retaining a high adhesion even with the lapse of time and resisting a severe treatment such as retort sterilization. When this paint is applied to a bonded can, leakage of the content from the side seam with the lapse of time can be effectively prevented. When this paint is applied to a can provided with an easy-open can lid, occurrence of the enamel feather can be prevented at the time of opening the lid.

What we claim is: 
     
       1. A paint for cans which comprises (1) an epoxy resin component formed by condensation of a dihydroxyl compound with an epihalohydrin and (2) a curing agent component, said epoxy resin component containing terminal α-glycol groups at a concentration of 0.05 to 0.60 equivalents per Kg of the resin, and terminal epoxy groups at a concentration of 0.20 to 1.80 equivalents per Kg of the resin. 
     
     
       2. A paint as set forth in claim 1 wherein the epoxy resin component is an epoxy resin in which the terminal α-glycol groups and the terminal epoxy groups are present at a molar ratio in the range of from 5/95 to 75/25. 
     
     
       3. A paint as set forth in claim 1 or 2 wherein the epoxy resin component is an epoxy resin represented by the following general formula: ##STR9## wherein R stands for a divalent residue formed by removing two hydroxyl groups from a dihydroxyl compound, espccially an alkylene or arylene group having 2 to 20 carbon atoms or a combination thereof, Y stands for ##STR10## or a hydrogen atom, with the proviso that the following conditions (a) to (d) are satisfied: (a) the concentration of ##STR11## is 0.05 to 0.60 equivalent per Kg of the resin, (b) the concentration of ##STR12## is 0.20 to 1.80 equivalents per Kg of the resin, (c) the molar ratio of ##STR13## is in the range of from 5/95 to 75/25 and (d) terminal hydroxyl groups derived from a dihydroxyl compound may be present in an amount of up to 50 mol % based on the total terminal groups, and n is a number selected so that the number average molecular weight of the resin is 900 to 5500. 
     
     
       4. A paint as set forth in claim 1 wherein the epoxy resin component is an epoxy resin formed by condensation of an epihalohydrin with bisphenol A or bisphenol B. 
     
     
       5. A solution-type can paint as set forth in claim 1 wherein the curing agent component is a resinous curing agent selected from the group consisting of phenol-formaldehyde resins, urea-formaldehyde resins, malamine-formaldehyde resins, acrylic resins, alkyd resins and polyamide resins and the resinous curing agent is present in an amount of 5 to 60% by weight based on the epoxy resin component. 
     
     
       6. A powdery can paint as set forth in claim 1 wherein the curing agent component is an acid anhydride or dicyandiamide and is present in an amount of 3 to 40% by weight based on the solid epoxy resin component. 
     
     
       7. A coated metal can which is coated and baked at least on the inner face of a can lid or can body with the paint as set forth in claim 1.